Automated longitudinal position translator for ultrasonic imaging probes, and methods of using same

ABSTRACT

An improved medical imaging system preferably includes an imaging device having a housing, an imaging transducer, and a position marker coupled near the imaging transducer. The system further includes a motor capable of driving the imaging transducer in a generally longitudinal direction relative to the housing. Data obtained from tracking the position marker may be cross-correlated with data obtained from the imaging transducer. In one aspect, the position marker may be a sensor capable of communicating with a medical positioning system.

CROSS-REFERENCE TO RELATED PATENTS AND APPLICATIONS

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 10/138,477, which is a continuation of U.S. patent application Ser.No. 09/794,543, filed Feb. 26, 2001, now U.S. Pat. No. 6,409,672, whichis a continuation of U.S. patent application Ser. No. 09/397,836, filedSep. 16, 1999, now U.S. Pat. No. 6,193,736, which is a continuation ofU.S. patent application Ser. No. 09/040,058, filed Mar. 17, 1998, nowU.S. Pat. No. 6,013,030, which is a continuation of U.S. patentapplication Ser. No. 08/747,773, filed Nov. 13, 1996, now U.S. Pat. No.5,759,153, which is a continuation of U.S. patent application Ser. No.08/573,507, filed Dec. 12, 1995, now U.S. Pat. No. 5,592,942, which is acontinuation of U.S. patent application Ser. No. 08/285,969, filed Aug.4, 1994, now U.S. Pat. No. 5,485,846, which is a continuation of U.S.patent application Ser. No. 7/906,311, filed Jun. 30, 1992, now U.S.Pat. No. 5,361,768, and also is a continuation-in-part of U.S. patentapplication Ser. No. 10/401,901, entitled “An Improved ImagingTransducer Assembly,” filed on Mar. 28, 2003, all of which are expresslyincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

[0002] The field of the invention generally relates to elongate medicalprobe assemblies and more particularly, to elongate medical probeassemblies of sufficiently miniaturized dimensions so as to be capableof navigating tortuous paths within a patient's organs and/or vessels.

BACKGROUND OF THE INVENTION

[0003] Probe assemblies having therapeutic and/or diagnosticcapabilities are being increasingly utilized by the medical community asan aid to treatment and/or diagnosis of intravascular and other organailments. In this regard, U.S. Pat. No. 5,115,814 discloses anintravascular probe assembly with a distally located ultrasonic imagingprobe element which is positionable relative to intravascular sites.Operation of the ultrasonic element in conjunction with associatedelectronic components generates visible images that aid an attendingphysician in his or her treatment of a patient's vascular ailments.Thus, a physician may view in real (or essentially near real) timeintravascular images generated by the ultrasonic imaging probe elementto locate and identify intravascular abnormalities that may be presentand thereby prescribe the appropriate treatment and/or therapy.

[0004] The need to position accurately a distally located operativeprobe element relative to an intravascular site using any therapeuticand/or diagnostic probe assembly is important so that the attendingphysician can confidently determine the location of any abnormalitieswithin the patient's intravascular system. Accurate intravascularposition information for the probe assembly will also enable thephysician to later replicate probe positions that may be needed forsubsequent therapeutic and/or diagnostic procedures, such as to enablethe physician to administer a prescribed treatment regimen over timeand/or to later monitor the effects of earlier therapeutic procedures.

[0005] Recently ultrasonic imaging using computer-assistedreconstruction algorithms has enabled physicians to view arepresentation of the patient's interior intravascular structures in twoor three dimensions (e.g., so-called three dimensional or longitudinalview reconstruction). In this connection, the current imagereconstruction algorithms employ data-averaging techniques which assumethat the intravascular structure between an adjacent pair of datasamples will simply be an average of each such data sample. Thus, thealgorithms use graphical “fill in” techniques to depict a selectedsection of a patient's vascular system under investigation. Of course,if data samples are not sufficiently closely spaced, then lesions and/orother vessel abnormalities may in fact remain undetected (i.e., sincethey might lie between a pair of data samples and thereby be “masked” bythe image reconstruction algorithms mentioned previously).

[0006] In practice, it is quite difficult for conventional ultrasonicimaging probes to obtain sufficiently closely spaced data samples of asection of a patient's vascular system under investigation since thereconstruction algorithms currently available depend upon the software'sability to process precisely longitudinally separated data samples. Inthis regard, conventional intravascular imaging systems depend uponmanual longitudinal translation of the distally located ultrasoundimaging probe element by an attending physician. Even with the mostskilled physician, it is practically impossible to manually exerciseconstant rate longitudinal translation of the ultrasound imaging probe(which thereby provides for a precisely known separation distancebetween adjacent data samples). In addition, with manual translation,the physician must manipulate the translation device while observing theconventional two dimensional sectional images. This division of thephysician's attention and difficulty in providing a sufficiently slowconstant translation rate can result in some diagnostic informationbeing missed. In order to minimize the risk that diagnostic informationis missed, it is necessary to devote more time to conducting the actualimaging scan which may be stressful to the patient.

[0007] Thus, what has been needed in this art is an imaging probeassembly which is capable of being translated longitudinally within asection of a patient's vascular system at a precise constant rate. Suchan ability would enable a series of corresponding precisely separateddata samples to be obtained thereby minimizing (if not eliminating)distorted and/or inaccurate reconstructions of the ultrasonicallyscanned vessel section (e.g., since a greater number of more closelyspaced data samples could reliably be obtained). Also, such an assemblycould be operated in a “hands-off” manner which would then allow thephysician to devote his attention entirely to the real time images withthe assurance that all sections of the vessel were displayed. In termsof reconstruction, the ultrasound imaging probe could be removedimmediately and the physician could interrogate the images or theiralternative reconstructions on a near real time basis. Such a feature isespecially important during coronary diagnostic imaging since minimaltime would be needed to obtain reliable imaging while the blood flowthrough the vessel is blocked by the probe assembly.

SUMMARY OF THE INVENTION

[0008] The preferred embodiment of the improved medical imaging systemincludes an imaging device having a housing, an imaging transducerassembly, and a position marker coupled near the imaging transducerassembly. The system further includes a motor capable of driving theimaging transducer in a generally longitudinal direction relative to thehousing.

[0009] In the preferred embodiment, automated units are connectable to aprobe assembly having a distally located ultrasound transducersubassembly which enables the transducer subassembly to be positionedaccurately by an attending physician and then translated longitudinally(relative to the axis of the elongate probe assembly) within the patientunder automated control. The data obtained from tracking the positionmarker may be cross-correlated with data obtained from the imagingtransducer assembly. As an option, the position marker may be a sensorcapable of communicating with a medical positioning system.

[0010] Other systems, methods, features and advantages of the inventionwill be or will become apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description, be within the scope ofthe invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to better appreciate how the above-recited and otheradvantages and objects of the inventions are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof, which are illustrated in theaccompanying drawings. It should be noted that the components in thefigures are not necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention. Moreover, in the figures,like reference numerals designate corresponding parts throughout thedifferent views. However, like parts do not always have like referencenumerals. Moreover, all illustrations are intended to convey concepts,where relative sizes, shapes and other detailed attributes may beillustrated schematically rather than literally or precisely.

[0012]FIG. 1 is a schematic view of an example embodiment of anultrasonic imaging system that includes an automated longitudinalposition translator;

[0013]FIG. 2 is a top plan view of an example embodiment of the probedrive module employed with the longitudinal position translator showingthe housing thereof in an opened state;

[0014]FIG. 3 is a side elevation view, partly in section, of the probedrive module shown in FIG. 2;

[0015]FIGS. 4A and 4B are each side elevation views of the longitudinalposition translator of FIGS. 1-2 in its automated and manual conditions,respectively;

[0016]FIGS. 5A and 5B are each top plan views of the longitudinalposition translator of FIGS. 1-2 in its automated and manual conditions,respectively;

[0017]FIGS. 6A and 6B are each front end elevational views of thelongitudinal position translator of FIGS. 1-2 in its automated andmanual conditions, respectively;

[0018]FIG. 7 is a partial side elevational view which is also partly insection of the longitudinal position translator of FIGS. 1-2;

[0019] FIGS. 8A-8C are top plan views of the longitudinal positiontranslator of FIGS. 1-2 which schematically depict a preferred mode ofautomated operation;

[0020]FIG. 9A is an illustration of a prior art medical positioningsystem;

[0021]FIG. 9B is a simplified diagram of an electrical circuit formed bya sensor of a prior art medical positioning system;

[0022]FIG. 10A is cross-sectional side view of an imaging transducerassembly in accordance with an exemplary embodiment of the invention;

[0023]FIG. 10B is a cross-sectional view of a coaxial cable within theimaging transducer assembly of FIG. 10A; and

[0024]FIG. 10C is a simplified diagram of an electrical circuit formedby the imaging transducer assembly of FIG. 10A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] A schematic diagram of an exemplary ultrasound imaging system 10is shown in accompanying FIG. 1. System 10 generally includes anultrasound imaging probe assembly 12 having a guide sheath 14 and adistally located ultrasound imaging probe element 16 inserted into thelumen of guide sheath 14, the probe element 16 being depicted in FIG. 1as being visible through the guide sheath's transparent. The ultrasonicimaging probe assembly 12 preferably embodies those features more fullydescribed in the above-identified U.S. Pat. No. 5,115,814.

[0026] The overall length of the imaging probe assembly 12 is suitablefor the desired diagnostic and/or therapeutic intravascular procedure.For example, the overall length of the probe assembly 12 may be shorterfor direct (e.g., arteriotomy) insertions as compared to the length ofthe probe assembly 12 needed for percutaneous distal insertions (e.g.,via the femoral artery). A representative length of the imaging probeassembly 12 is therefore shown in the accompanying drawings for clarityof presentation.

[0027] The terminal end of the guide sheath 14 preferably carries aradiopaque marker band 18 formed of gold or other fluoroscopicallyvisible material. The marker band 18 allows the attending physician tomonitor the progress and position of the guide sheath 14 duringintravascular insertions using standard fluoroscopic imaging techniques.

[0028] The proximal end of the imaging probe assembly 12 is receivedwithin a probe drive module 20. In essence, the probe drive moduleincludes a distally open-ended and longitudinally barrel-shaped housing22, and a positioning lever 24 which captures the proximal end of theguide sheath 14. The proximal end of the ultrasound imaging probeelement 16 is mechanically and electrically connected to the probe drivemodule 20. Longitudinal reciprocal movements of the positioning lever 24relative to the housing 22 will thus in turn effect relativelongitudinal displacements of the distal end of the probe element 16within the guide sheath 14 relative to the longitudinal axis of theprobe assembly 12.

[0029] The probe drive module 20 also includes a drive unit 26 fixedlyconnected proximal to the housing 22 and contains the structures whichsupply mechanical rotation and electrical signals to the probe element16. In the preferred embodiment, mechanical rotation of the probeelement 16 is provided by a separate precision motor 28 associated witha base unit (not shown) and operatively coupled to the probe drivemodule 20 via a flexible drive cable 28 a. It is entirely conceivable,however, that the drive unit 26 could be sized so as to accommodate themotor 28.

[0030] The drive unit 26 is most preferably configured so that theattending physician may comfortable grasp its exterior with one handwhile the probe drive module 20 is in its manual condition. The driveunit 26 thus forms a handle which allows the physician to manuallymanipulate the relative position between the housing 22 and thepositioning lever 24 thereby responsively permitting manual longitudinalmovements to be imparted to the probe element 16. A thumb/finger switch30 may thus be manually depressed to allow the physician to selectivelyoperate the drive unit 26 and thereby rotate the ultrasonic imagingprobe element 16 when it is desired to conduct an ultrasonic imagingscan. Electrical connection between the switch 30 and the controlconsole 46 is made via I/O cabling 41.

[0031] During rotation, electrical communication is established betweenthe transducer subassembly in the distal end of the ultrasonic imagingprobe element 16 and the ultrasound transceiver 40 via patient-internalelectrical coaxial cabling (not shown) within the probe element 16,drive unit 26 and electrical patient-external I/O cabling 41. Theultrasound transceiver 40 produces a pulse signal (of desired magnitudeand shape) which is applied via the electrical cabling 41 to anelectroacoustic transducer associated with the distal end of the probeelement 16. The transceiver 40 also performs conventional signalprocessing operations (e.g., amplification, noise reduction and thelike) on electrical signals generated by the electro-mechanicalexcitation of the transducer within the probe element 16 (i.e., signalsgenerated by the transducer in response to receiving acoustic echowaves).

[0032] These signals are further processed digitally via known displayalgorithms (e.g., conventional PPI (radar) algorithms) and are thensupplied as input to a CRT monitor 42 (or any other equivalent displaydevice) so as to generate an ultrasound image 44 of desired formatrepresentative of the vascular structures reflecting ultrasonic energytoward the transducer within the distal end of the probe element 16. Acontrol console 46 may be employed by the attending physician so as toselect the desired operational parameters of the ultrasound transceiver40 and/or the display format of the image 44 on the CRT 42, for example.

[0033] The probe drive module 20 is operatively coupled to and supportedby the linear translation module 48 so as to allow for reciprocalrectilinear movements of the housing 22/drive unit 26 relative to boththe linear translation module 48 and the positioning arm 24 whichcollectively remain in a fixed position as will be described in greaterdetail below. As will also be described in greater detail below, theprobe drive module 20 is mounted for hinged movements relative to thelinear translation module 48 between a manually-operable condition(whereby the probe drive module 20 is operatively disengaged from themotor driven translator associated with the linear translation module48) and a automatically-operable condition (whereby the probe drivemodule 20 is operatively engaged with the motor driven translatorassociated with the linear translation module 48).

[0034] The linear translation module 48 includes a proximal housing 48 awhich contains appropriate speed-reducers, drive shafts and associatedcouplings to be described below in connection with FIG. 7. Suffice it tosay here, however, that driven power is provided to the structuresinternally of housing 48 a by a separated precision motor 50 associatedwith a system base unit (not shown) which is coupled operatively to thestructures internally of housing 48 a via a flexible drive shaft 50 a.Again, it is entirely conceivable that the housing 48 a of the lineartranslation module 48 could be sized and configured so as to accommodatethe motor 50. Automated operation of the motor 50 (and hence the lineartranslation module 48) may be accomplished through the selection ofappropriate operation parameters by the attending physician via controlconsole 46. Operation of both the linear translation module 48 and theprobe drive module 20 may be initiated by depressing the foot-switch 27.

[0035] The exemplary probe drive module 20 is perhaps more clearlydepicted in accompanying FIGS. 2 and 3. As is seen, the housing 22 iscollectively formed by a pair of elongate lower and upper housingsections 51, 52, respectively, which are coupled to one another alongadjacent longitudinal edges in a clamshell-hinged arrangement via hingepin 54.

[0036] It will be noticed with particular reference to FIG. 2 that theproximal and distal ends 54 a, 54 b of pin 54 are rigidly fixed to theproximal and distal ends 51 a, 51 b of housing section 51, respectively,while the housing section 52 is pivotally coupled to the pin 54 (andhence the housing section 51) by means of proximal and distal andintermediate pivot sleeves 56 a, 56 b and 56 c, respectively. Thehousing sections 51, 52 are maintained in their closed state (i.e., asshown in FIGS. 4A through 5B) by means of a spring-loaded detent 57 a(see FIG. 2) which may be moved into and out of an aperture (not shown)formed in the housing section 51 via operating lever 57 b.

[0037] The positioning lever 24 is oriented transversely relative to theelongate axis of housing 22. In this regard, the lever 24 includes asleeve end 24 a which is coupled to the pivot pin 54 to allow reciprocallongitudinal and pivotal movements of the lever 24 to occur relative tothe longitudinal axis of pin 54. The opposite end 24 b of lever 24extends radially outward from the housing 22.

[0038] The housing 22 defines an elongate slot 58 when the housingsections 51, 52 are in a closed state (i.e., as depicted in FIG. 1). Theslot 58 allows the positioning lever 24 to be manually moved along thelongitudinal axis of pin 54 during use (i.e., when the housing sections51, 52 are in a closed state) between retracted and extended positions(shown respectively by phantom line representations 24′ and 24″ in FIG.2). The retracted position 24′ of lever 24 is established by a distalface of a pivot sleeve 56 c integral with the housing section 52 andpivotally coupled to pin 54 in a manner similar to pivot sleeves 56 aand 56 b. On the other hand, the extended position 24″ of lever 24 isestablished by a proximal face of pivot sleeve 56 b.

[0039] The lever 24 is supported by a concave inner surface 59 formed inthe housing section 51 when the housing sections 51 and 52 are in aclosed state. The inner surface 59 provides a bearing surface againstwhich the lever 24 slides during the latter's movement between itsretracted and extended positions 24′ and 24″, respectively.

[0040] A scale 60 (see FIGS. 4A and 5A) preferably is provided on thehousing 22. A pointer 24 c associated with the lever 24 may be alignedwith the scale 60 to provide an attending physician with informationregarding the position of probe element 16 relative to its most distalposition within the guide sheath 14. That is, longitudinal movement oflever 24 an incremental distance (as measured by pointer 24 c and thescale 60) will effect movement of the probe element 16 relative to itsmost distal position within the guide sheath's distal end by that sameincremental dimension.

[0041] Accompanying FIG. 2 also more clearly shows the cooperativeengagement between positioning lever 24 and the proximal end of guidesheath 14. In this regard, it will be noted that the proximal end ofguide sheath 14 includes a side-arm port 70 which extends generallytransverse to the longitudinal axis of guide sheath 14. Side-arm port 70includes a conventional Leur-type locking cap 72 that is coupledcoaxially to a similar locking cap 74 associated with the proximal endof guide sheath 14. Side-arm port 70 is thus in fluid-communication withthe lumen of guide 14 so that saline solution, for example, may beintroduced via side arm tubing 70 a.

[0042] A shaft extension 75 of probe element 16 and electrical cablingcoaxially carried thereby are mechanically and electrically coupled tothe output shaft 77 of the probe drive module 20 via coaxial cablecouplings 75 a and 75 b. It will be appreciated that coaxial cablingwithin the flexible torque cable portion of probe element 16 (not shown)will rotate with it as a unit during operation, but that the electricalI/O signals will be transferred to transceiver 40 by means of couplings75 a and 75 b. The manner in which the separate electrical I/O path(represented by cable 41—see FIG. 1) and mechanical input path(represented by the flexible drive shaft 28 a—see FIG. 1) are combinedinto a common electrical/mechanical output path (represented by outputshaft 77) will be explained in greater detail with reference to FIG. 3.

[0043] The shaft extension 75 is preferably fabricated from a length ofconventional stainless steel hypodermic tube and is rigidly coupled atits distal end to a flexible torque cable (not shown). As mentionedbriefly above, the torque cable extends the length of the guide sheath14 and is connected at its distal end to a transducer subassembly in thedistal end of the probe element 16. The torque cable thereby transfersthe rotational motion imparted via the motor to shaft extension 75 ofthe probe element 16 causing the transducer subassembly to similarlyrotate within the lumen of the guide sheath 14 near the guide sheath'sdistal end, as well as to be longitudinally shifted within guide sheath14 via manipulation of the relative position of the arm 24.

[0044] The shaft extension 75 extends through an end cap 76 which iscoupled coaxially to locking caps 72 and 74. End cap 76 houses asynthetic resin bearing element (not shown) which serves as a proximalrotational bearing for the shaft 75, and also serves to seal theproximal end of guide sheath 14 against fluid (e.g., saline liquid)leakage.

[0045] Lever 24 defines a pair of mutually transverse concave cradlesurfaces 80 and 82. The longitudinal dimension of cradle surface 80 isoriented parallel to the longitudinal dimension of housing 22, whereascradle surface 82 (which is joined at one of its ends to the cradlesurface 80) is oriented transverse to the longitudinal dimension ofhousing 22 (i.e., since it is traverse to cradle surface 80).

[0046] Cradle surface 80 is sized and configured so as to accommodate anexterior surface portion of coaxially locked caps 72, 74 and 76. Cradlesurface 82, on the other hand, is sized and configured to acceptside-arm port 70 and side-arm tubing 70 a extending therefrom. Anaxially extending inner concave surface 84 is defined in housing section52 and, like cradle surface 82, is sized and configured so as to acceptan exterior portion of locking caps 72, 74 and 76.

[0047] When housing sections 51 and 52 are in a closed state, caps 72,74 and 76 will be enveloped by housing 22. More specifically, innerconcave surface 84 will positionally restrain caps 72, 74 and 76 withincradle surface 80 when housing sections 51 and 52 are closed. Sinceside-arm port 70 will likewise be positionally restrained within cradlesurface 82 when housing sections 51, 52 are closed, caps 72, 74 and 76will be moved longitudinally as a unit with position lever 24. That is,longitudinal movements of lever arm 24 between its retracted andextended positions will cause the proximal end of guide sheath 14 (i.e.,coaxially mounted caps 72, 74 and 76) to be longitudinally movedrelative to the longitudinally stationary (but axially rotatable) shaftextension 75. In such a manner, the proximal end of guide sheath 14 willbe moved closer to and farther from the open distal end of housing 22.

[0048] As can be seen in FIG. 3, the interior of the drive unit 26 ishollow to house electrical/mechanical coupling assembly 85.Electrical/mechanical coupling 85 combines an electrical inputpath—represented by coaxial I/O cable 41 which establishes electricalcommunication with transceiver 40—and a mechanical inputpath—represented by flexible drive shaft 28 a associated with motor 28(see FIG. 1) into a common coaxial output shaft 77.

[0049] Output shaft 77 is rotatably held within bearing block 86 andincludes a rearwardly extending rotatable tail portion carrying a numberof electrical slip-rings 86 a. Electrical communication between theslip-rings 86 a and, coupling 75 b is established by a length of coaxialcable (not shown) housed within the output shaft 77. Stationary brushes88 a in sliding electrical contact with respective ones of theslip-rings 86 a are associated with a brush block 88. Lead wires 88 bare, in turn, coupled electrically at one end to brush block 88 (andhence to coaxial connector 75 a via brushes 88 a and slip-rings 86 a),and at the other end to coaxial I/O cable 41 via a ferrite coiltransformer (not shown). Slip-rings 86 a, brush 88 a, brush block 88,lead wires 88 b, and ferrite core transformer (not shown) are housedwithin a common electrically shielded enclosure 90.

[0050] The mechanical input path generally represented by flexible driveshaft 28 a is coupled operatively to one end of a rigid rotatable driveshaft 92 carrying a drive gear 94 at its other end. Drive gear 94 is, inturn, meshed with a gear 96 carried by output shaft 77. Upon rotation ofdrive shaft 92, meshed gears 94, 96 will cause shaft 77 to responsivelyrotate. Preferably, gears 94 and 96 are in a 1:1 ratio, but other gearsizes (and hence ratios) may be provided if desired.

[0051] The probe drive unit 20 is mounted for reciprocal rectilinearmovements to the linear translation module 48 as is shown inaccompanying FIGS. 4A through 6B. In this regard, the linear translationmodule includes a base plate 100 which supports the housing 48 a and itsinternal structures (to be described below with reference to FIG. 7).The probe drive module 20 itself includes a longitudinally spaced-apartpair of support flanges 102, 104, each of which is slidably mounted ontoa pair of parallel guide rails 106, 108.

[0052] The proximal end of guide rail 106 is pivotally connected to thehousing 48 a while its distal terminal end is pivotally connected to anupright support block 106 a. A forward and rearward pair of transversesupport arms 110, 112 each having one end rigidly coupled to guide rail106 and an opposite end rigidly coupled to the guide rail 108. Thus, thesupport arms 110, 112 are capable of pivoting between a lowered position(e.g., as shown in FIGS. 4A, 5A and 6A) and a raised position (e.g., asshown in FIGS. 4B, 5B and 6B) by virtue of the pivotal guide rail 106 soas to, in turn, pivotally move the probe drive module 20 between itsautomatically-operable condition and its manually-operable condition,respectively, due to its attachment to the guide rails 106, 108 viasupport flanges 102, 104.

[0053] The ends of each transverse support arm 110, 112 between whichthe guide rail 108 is fixed are removably captured by uprightrestraining posts 114, 116, respectively. As is perhaps more clearlyshown in FIGS. 6A and 6B, the restraining posts 114, 116 (onlyrestraining post 114 being visible in FIGS. 6A and 6B) are rigidlysupported by the base plate 100 and include an inwardly projecting lip114 a, 116 a which provide an interference fit with the terminal ends ofsupport arms 110, 112, respectively. In this connection, it is preferredthat the restraining posts 114, 116 be formed of a relatively stiff, butresilient plastics material (e.g., nylon, polyacetal or the like) sothat when the probe drive unit is moved between itsautomatically-operable and manually-operable conditions, the posts 114,116 are capable of yielding somewhat to allow such movement.

[0054] The positioning arm 24 of the probe drive unit 20 is fixedly tiedto the forward transverse support arm 110 by an upright connector 120 aon a longitudinal connector 120 b. In this regard, the upper end ofupright connector 120 a extends through a longitudinal slot on the sideof the housing 22 opposite slot 58 and positionally captures the ends ofthe positioning arm 24 around pin 54. The lower end of the uprightconnector 120 a is connected to the distal end of the horizontallydisposed longitudinal connector 120 b. The proximal end of longitudinalconnector 120 b is, in turn, rigidly fixed to the transverse support arm110 by any suitable means (e.g., screws). It will be understood,therefore, that the position of the positioning arm 24 (and hence theguide sheath 14) remains fixed relative to the base 100 of the lineartranslation module 48 during longitudinal movements of the probe drivemodule 20 along the guide rails 106 and 108. Thus, the relative positionof the patient-internal transducer subassembly at the distal end of theprobe element 16 will correspondingly shift the same distance as theprobe drive module 20 relative to the patient internal distal end of theguide sheath 14.

[0055] Automated longitudinal shifting of the probe drive module 20 (andhence the ultrasonic transducer at the distal end of the probe element16) is permitted by the coaction between a longitudinally extendingdrive screw 120 and a threaded collar portion 122 (see FIGS. 4B and 7)associated with the support flange 102 of the probe drive module 20. Thedistal and proximal ends of the drive screw 120 are rotatably supportedby an upright distal bearing block 124 and an upright proximal bearingblock 126 (see FIG. 7), respectively.

[0056] As can be seen in FIGS. 4B, 5B, 6B and 7, the threaded collarportion 122 is disengaged from the threads of drive screw 120 when theprobe drive module 20 is in its manually-operable condition. As aresult, the attending physician may simply manually shift the probedrive module 20 longitudinally along the guide rails 106, 108. When theprobe drive module 20 is pivoted into its automatically-operablecondition as shown in FIGS. 4A, 5A and 6A, the threads associated withthe threaded collar portion 122 will be mateably engaged with thethreads of the drive screw 120. As a result, rotation of the drive screw120 about its longitudinal axis will translate into longitudinaldisplacement of the probe drive module 20. The threads of the drivescrew 120 and the threaded collar portion 122 as well as the rotationdirection of the drive screw 120 are most preferably selected so as toeffect longitudinal shifting of the probe drive module from the distalend of the drive screw towards the proximal end thereof—i.e., a distalto proximal displacement. However, these parameters could be changed soas to effect a reverse (proximal to distal) displacement of the probedrive unit, if necessary or desired.

[0057] The drive screw 120 is coupled operatively to the flexible driveshaft 50 a (and hence to the driven output of motor 50) by thestructures contained within housing 48 a. In this regard, the proximalend of the drive screw is coupled to the output shaft of a speed reducer128 via a shaft coupling 130. The input to the speed reducer 128 is, inturn, coupled to the flexible drive shaft 50 a from a rigid shaftextension member 132 and its associated shaft couplings 132 a and 132 b.The speed reducer 128 is of a conventional variety which provides apredetermined reduced rotational speed output based on the rotationalspeed input. Preferably, the motor 50, speed reducer 128 and drive screw120 are designed so as to effect longitudinal translation of the probedrive unit 20 at a rate of between about 0.25 to 1.0 mm/sec. Of course,other longitudinal translation rates may be provided by varying theparameters of the motor 50, speed reducer 128 and/or drive screw 120.

[0058] In use, the attending physician will preposition the guide sheath14 and imaging probe element 16 associated with the ultrasound imagingprobe assembly 12 within the vessel of the patient to be examined usingstandard fluoroscopic techniques and/or the techniques disclosed in theabove-mentioned U.S. Pat. No. 5,115,814. Once the guide sheath 14imaging probe element 16 have been prepositioned in a region of thepatient's vessel which the physician desires to observe, the proximalend of the probe assembly 12 will be coupled to the probe drive module20 in the manner described above. Thereafter, the physician may conductan ultrasound scan of the patient's vessel by operating switch 30 tocause high-speed rotation of the transducer subassembly on the distalend of the probe element 16 within the guide sheath 14. Data samplesassociated with different transverse sections of patient's vessel maythen be obtained by the physician manually shifting the probe drivemodule 20 along the guide rails 106, 108 in the manner described above.

[0059] Alternatively, the physician may elect to pivot the probe drivemodule 20 into its automatically-operable condition and then selectautomated operation of the same via the control console 46 andfoot-switch 27. In such a situation, the probe drive module (and hencethe transducer subassembly at the distal end of the probe element 16)will be shifted longitudinally at a constant rate simultaneously withhigh-speed rotation of the transducer subassembly. In this manner, datasamples representing longitudinally spaced-apart 360 degree. slices” ofthe patient's interior vessel walls will be accumulated which can thenbe reconstructed using known algorithms and displayed in“two-dimensional” or “three-dimensional” formats on the monitor 42.

[0060] Accompanying FIGS. 8A-8C schematically depict the longitudinaltranslator being operated in an automated manner. In this connection,and as was noted briefly above, the probe drive module 20 is mostpreferably translated in a distal to proximal direction by means of thelinear translation module 48 (i.e., in the direction of arrows 140 inFIGS. 8A and 8B). In FIG. 8A, the probe drive module is shown in aposition at the beginning of an automated ultrasonic imaging scan, itbeing noted that the pointer 24 c associated with the positioning arm 24registers with the zero marking on the scale 60. The physician will theninitiate automated ultrasonic scanning via the foot-switch 27 whichcauses the probe drive unit 20 to be displaced proximally (arrow 140) ata constant rate as shown in FIG. 8B. This proximal displacement of theprobe drive module 20 will, in turn, cause the transducer subassembly onthe distal end of the probe element 16 to be longitudinally displacedproximally (i.e., pulled back away from) the distal-most end of theguide sheath 14.

[0061] The ultrasonic imaging scan is automatically terminated (e.g., byuse of suitable limit switches and/or position transducers) when theprobe drive unit reaches its most proximal position as shown in FIG. 8C.In this connection, most preferably a limit switch (not shown) isprovided enclosed within a limit switch housing 29 (see FIGS. 4a and 5B)which is mechanically actuated when support flange 102 contacts supportarm 112 (i.e., when the probe drive module 20 is in its most proximalposition). The limit switch in housing 29 communicates electrically withthe control console 46 via cabling 41. Virtually any suitable equivalentposition-sensing devices could be employed in place of the limit switch.For example, the housing 29 could be sized and configured to accommodatean absolute position transducer so as to communicate absolute positionto the control console 46. The information provided by such an absoluteposition transducer could be employed in conjunction with modifiedreconstruction algorithms for image reconstruction, even during manualoperation of the probe drive module 20.

[0062] Upon the probe drive module 20 reaching its most proximalposition, the pointer 24 c associated with the positioning arm 24registers with the marking “10” on the scale 60 of housing 22. Ofcourse, the ultrasonic imaging scan need not necessarily be conductedover the entire range of 0-10 marked on the scale 60 and thus could beterminated at any time by the physician simply releasing the foot-switch27 or by simply pivoting the probe drive module 20 into itsmanually-operable condition.

[0063] Those skilled in this art will recognize that a number ofequivalent mechanical and/or electrical means could be employed. Forexample, locking slides, latches and quarter-turn screws could be usedto allow engagement and disengagement of the probe drive module with thelinear translation module. A flexible drive shaft connects the lineartranslation module to a rate-controlled motor which controls theautomatic linear translation rate. The motor is most preferably locatedin a separate fixed base unit, but could be provided as in an integralpart of the linear translation module, if desired.

[0064] Furthermore, various translation rates associated with the motormay be selected for various purposes. For example, slow rates give ampletime for the physician to examine the real-time images in cases wheretime is not a limiting factor. The rate upper limit is governed by theprobe rotation rate and the effective thickness of the imaging dataslices generated by the probe, such that there is no (or an acceptable)gap between successive imaging data slices. This would prevent missingdiscernible features during vascular imaging with automatic translation.The effective thickness is governed by the ultrasonic beamcharacteristics of the probe. For some applications, the translation maybe discontinuous (i.e., gated to an electrocardiogram) for use withmodified algorithms or programmed to translate a fixed distancediscontinuously.

[0065] As mentioned above, referring back to FIG. 1, the terminal end ofthe guide sheath 14 may include a radiopaque marker band 18 formed ofgold or other fluoroscopically visible material. The marker band 18allows the longitudinal progress and position of the guide sheath 14 tobe monitored. Accordingly, whether the probe drive module 20 is in itsmanual condition or its automatically-operable condition, as describedabove, the longitudinal progress, or position, of the guide sheath 14may be cross-correlated with data obtained from the transducersubassembly of the imaging probe element 16. Thus, not only may thecross-sectional image of a blood vessel be obtained, but also thethree-dimensional longitudinal profile of the same blood vessel.

[0066] Alternatively, or in addition to, the radiopaque marker band 18,electromagnetic and/or electro-mechanical signals may be utilized tomonitor the longitudinal progress and position of the guide sheath 14.For example, there may be an antenna wrapped around the housing of theimaging device, where the antenna transmits electromagnetic signals tobe received by an external receiver (e.g., active transmission) or theantenna is otherwise detectable (e.g., passive) by an external receiver.Such approaches are described in U.S. patent application Ser. No.10/401,901, entitled “An Improved Imaging Transducer Assembly,” filed onMar. 28, 2003, which is hereby incorporated by reference in itsentirety.

[0067] One approach to monitor the longitudinal progress and position ofthe guide sheath 14 is to incorporate a medical positioning system thatis generally known in the art. Turning to FIG. 9A, a prior art medicalpositioning system 240 is illustrated. The system 240 generally includesa plurality of transmitter and/or receiver nodes 250 that may bearranged around a patient. For instance, the nodes 250 may be arrangedon a framework of towers that surround a patient. The system 240 furtherincludes one or more sensors 260, which are configured to send and/orreceive electro-magnetic, or electro-mechanical, signals to and/or fromthe transmitter/receiver nodes 250.

[0068] A sensor 260, coupled with a guidewire (partially shown), may beplaced within the blood vessel of a patient's body. The signalsexchanged between the sensor 260 and the nodes 250 function asnavigational signals which, as can be appreciated by one of ordinaryskill in the art, may be used to determine the position of the sensor260 within the patient's body. In other words, the sensor 260 transmitsnavigational signals to the nodes 250, and a processor (not shown)coupled with the nodes 250 determines the position of the sensor 260based on the signals received by the nodes 250. Alternatively, or inaddition, the nodes 250 may send navigational signals to the sensor 260,and a processor (not shown) coupled with the sensor 260 determines theposition of the sensor 260 within the patient's body based on thesignals sent by the nodes 250. The medical positioning system 240 cantrack and record the position of the sensor 260 as it is movedthroughout a patient's blood vessel, thus providing a longitudinalprofile of the blood vessel.

[0069] Turning to FIG. 9B, the sensor 260 is depicted as a simplifiedelectrical circuit having two terminals, A and B, an “antenna” load, anda load 270. The antenna is the portion of the sensor 260 where asubstantial amount of the navigational signals are sent and/or received.If the sensor 260 is configured to send electromagnetic signals to thenodes 250, then to facilitate the electromagnetic broadcast, the load270 may be a voltage source 270, which charges the antenna via theterminals A and B. Alternatively, if the sensor 260 is configured toreceive electromagnetic signals from the nodes 250, then the load 270may be sensor circuitry, which may include a signal processor (notshown) to handle navigational signals.

[0070] In an example embodiment of an improved imaging system, a sensorof a medical positioning system may be combined with a transducersubassembly to form a transducer/sensor subassembly 300, as shown inFIGS. 10A and 10B. Turning to FIG. 10A, a cross-sectional side view of atransducer/sensor subassembly 300 is shown in a lumen 305 of the distalportion of a guidewire or catheter assembly (partially shown) having anouter tubular wall 301. The transducer/sensor subassembly 300 includes acoaxial cable 410, having a center conductor wire 420, and an outershield wire 430, as shown in FIG. 10B. The center conductor wire 420 isinsulated from the outer shield wire 430. In addition, the shield wire430 is surrounded by an insulating jacket 440. It should be noted thatnumerous alternative cable configurations may be used; for example, acable having “twisted pair” wires may be used instead of a coaxialcable.

[0071] Turning back to FIG. 10A, surrounding the coaxial cable 410 is alayer of insulating material, such as a non-conductive epoxy 330.Surrounding the epoxy 330 is a drive shaft 310, which is a conductivewire wound around the epoxy 330/coaxial cable 350 to form a first coilshape 310. Preferably, the conductive wire is stainless and has adiameter of approximately 500 microns. Thus, the coaxial cable 350 isconductively insulated from the drive shaft 310.

[0072] The distal end of the transducer/sensor subassembly 300 includesan electrically conductive backing material 390, having a top, bottomand center, which may be formed from an acoustically absorbent material(for example, an epoxy substrate having tungsten particles). The centerof the backing material 390 surrounds a shield pellet 400, which iselectrically coupled to the shield wire 430 at the distal end of thecoaxial cable 410. The top of the backing material 390 is coupled to thebottom of a layer of piezoelectric crystal (PZT) 380. The top of the PZTlayer 380 is coupled to a conductive acoustic lens 370, which mayinclude silver epoxy. The acoustic lens 370 is electrically coupled tothe center conductor wire 420 of the coaxial cable 410 via a connector360, which may include silver epoxy, surrounding the non-conductiveepoxy 330 such that the connector 360 is insulated from the backingmaterial 390.

[0073] The transducer/sensor subassembly 300 further includes a sensor320 of a medical positioning system. The “antenna” portion of the sensor320 is an insulated conductive wire 325. The wire 325 may also havemagnetic qualities. The wire 325 is tightly wrapped around a portion ofthe distal end of the coaxial cable 410 and non-conductive epoxy 330,and is also tightly wrapped around the distal end of the drive shaft310, forming a second coil shape. The second coil shape desirablyprovides an inductance for the antenna portion of the sensor 320 whencharged to increase its ability to send and receive electromagneticsignals. The second coil shape also serves as a housing to reinforce thetransducer/sensor subassembly 300. However, it should be noted that theantenna portion of the sensor 320 may have a variety of other shapes andconfigurations. For example, the antenna portion of the sensor 320 maybe a solid structure. The wire 325 is preferably copper andapproximately 10 microns in diameter. The small diameter of the wire 325allows the sensor 320 to have a small impact on the dimensions of thetransducer/sensor subassembly 300, thus allowing the transducer/sensorsubassembly 300 to still work within the lumen 305 of the guidewire orcatheter assembly.

[0074] The two ends of the wire 325 are terminals that receive anelectric charge. One end 350 of the wire 325 is coupled to the connector360 that electrically couples the acoustic lens 370 with the centerconductor wire 420 of the coaxial cable 410. The other end 340 of thewire 325 is coupled to the shield wire 430 of the coaxial cable 410,surrounded and insulated from the drive shaft 310 and the connector 360by the non-conductive epoxy 330.

[0075] To facilitate the operation of the imaging transducer portion ofthe transducer/sensor subassembly 300, the lumen 305 of the guidewire orcatheter assembly is preferably filled with a sonolucent media, such assaline. It is desirable to have at least one of the ends 350, 340 of thewire 325 of the sensor 320 be insulated from the saline within the lumen305 because if both ends, 350 and 340, were exposed to the saline, thesemi-conductive nature of the saline might shunt the ends, 350 and 340,thus undesirably “shorting out” the antenna of the sensor 320, and/oraffecting the signal-to-noise ratio of the navigational signals. Inlight of this, the transducer/sensor subassembly 300 preferably has oneend 340 of the wire 325 of the sensor insulated from the drive shaft310, backing material 390, connector 360, and saline by thenon-conductive epoxy 330. Further, the coil portion of the wire 325 isalso insulated from the driveshaft 310 and the saline in the lumen 305by a non-conductive material. The other end 350 of the wire 325,however, may be exposed to the saline.

[0076] During the operation of the transducer/sensor subassembly 300,the PZT crystal 380 is electrically excited by both the backing material390, charged through the shield wire 430, and the acoustic lens 370,charged through the center conductor wire 420. In addition, the antennaportion 325 of the sensor 320 is also charged by the shield wire 430 andthe center conductor wire 420. If the sensor 320 is configured to sendelectromagnetic signals to nodes of a medical positioning system (notshown), then the charge may facilitate a broadcast. However, if thesensor 320 is configured to receive electromagnetic signals from one ormore nodes of a medical positioning system (not shown), then separatecircuitry including a signal processor may be used to filter and extractthe desired electromagnetic signals. Thus, turning to FIG. 10C, thesubassembly 300 is depicted as a simplified electric circuit having avoltage source 530, the load of the PZT layer 380, the load of theantenna portion 325 of the sensor 320, which is in parallel with theload of the PZT layer 380, sensor circuitry 531, which may include asignal processor (not shown) to receive and process electromagneticsignals, i.e., navigational signals, from the sensor 320, as would beknown to a person of skill in the art, transducer circuitry 532, whichmay also include a signal processor (not shown) to process imagingsignals from the imaging transducer, and terminals A and B. Terminals Aand B represent the center conductor wire 420 and the shield wire 430 ofthe coaxial cable 410, respectively. Other features and circuits mayalso be added as desired.

[0077] In the foregoing specification, the invention has been describedwith reference to specific embodiments thereof. It will, however, beevident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention.For example, the reader is to understand that the specific ordering andcombination of process actions described herein is merely illustrative,and the invention can be performed using different or additional processactions, or a different combination or ordering of process actions. Forexample, this invention is particularly suited for applicationsinvolving medical imaging devices, but can be used on any designinvolving imaging devices in general. As a further example, each featureof one embodiment can be mixed and matched with other features shown inother embodiments. Additionally and obviously, features may be added orsubtracted as desired. Accordingly, the invention is not to berestricted except in light of the attached claims and their equivalents.

What is claimed is:
 1. A method for operating a catheter-deliveredimaging instrument having a housing, comprising the steps of:automatically translating the imaging instrument in a generallylongitudinal direction between spaced apart positions relative to thehousing within a lumen; obtaining positional data of the imaginginstrument during the translation of the imaging instrument; obtainingcross-sectional images of the lumen during the translation of theimaging instrument; cross-correlating the cross-sectional images withthe positional data.
 2. The method of claim 1, wherein the imaginginstrument is coupled with a radiopaque marker and the positional datais obtained by monitoring the radiopaque monitor.
 3. The method of claim1, wherein the imaging instrument is coupled with a medical positioningsensor, and the positional data is obtained by monitoring the medicalpositioning sensor.
 4. The method of claim 1, wherein the imaginginstrument is an ultrasonic imaging transducer.
 5. An imaging cathetercomprising: a motorized position translator coupled to a first end of acable; an imaging device coupled at or near the second end of the cable,the imaging device adapted for imaging within a patient's body; atracking device coupled near the imaging device, the tracking deviceadapted for tracking the position of the imaging device within thepatient's body; wherein the position translator is adapted for bothmanual linear translation of the cable relative to the catheter andmotor-driven linear translation of the cable relative to the catheterwhere during the motor-driven linear translation, the motorized positiontranslator controls the rate of longitudinal translation of the imagingdevice.
 6. The imaging catheter of claim 5, wherein the tracking devicecomprises a radiopaque marker band.
 7. The imaging catheter of claim 5,wherein the tracking device comprises an antenna capable of receivingelectromagnetic positioning signals.
 8. The imaging catheter of claim 5,wherein the tracking device is a sensor adapted to communicate with amedical positioning system.
 9. The imaging catheter of claim 8, whereinthe sensor includes an antenna portion having first and secondterminals.
 10. The imaging catheter of claim 9, wherein the imagingdevice and the sensor share the first and second terminals.
 11. Theimaging catheter of claim 8, wherein the imaging device has a first andsecond transducer terminal, the first transducer terminal being coupledto a first wire and the second transducer terminal being coupled to asecond wire, the imaging device and the sensor are coupled to the firstand second terminals, the first wire is coupled with one of the firstand second terminals and the second wire is coupled with the other ofthe first and second terminals.
 12. The imaging catheter of claim 5,wherein the imaging device is an ultrasound transducer.
 13. A medicalimaging system comprising: a medical positioning system; an imagingdevice adapted to be inserted into a lumen of a body, the imaging deviceincluding: a housing; a catheter having distal and proximal ends and alumen; an imaging transducer assembly located within the lumen of adistal portion of the catheter, the imaging transducer assemblyincluding an imaging transducer; and a sensor coupled to the imagingtransducer within the lumen of the catheter, the sensor adapted tocommunicate with the medical positioning system; a drive module thatrotates the imaging transducer assembly and has a translating mechanismto effect motor-driven longitudinal translation of the imaging device tolongitudinally shift the imaging transducer assembly betweenspaced-apart positions relative to the housing of the imaging device;and a clutch for switching between an automatically-operable conditionwherein the imaging transducer assembly is coupled to the translatingmechanism to effect the motor-driven longitudinal translation relativeto the housing of the imaging device, and a manually-operable conditionwherein the imaging transducer assembly is capable of beinglongitudinally shifted manually relative to the housing of the imagingdevice.
 14. The medical imaging system of claim 13, further comprising acomputing system for cross-correlating data obtained from the sensor anddata obtained from the imaging transducer assembly.
 15. The medicalimaging system of claim 13, wherein the imaging transducer assemblycomprises an acoustic lens coupled with a layer of piezoelectriccrystal, the piezoelectric crystal being coupled with a backingmaterial.
 16. The medical imaging system of claim 13, wherein thecatheter includes a driveshaft proximal to the imaging transducerassembly, and the sensor comprises a conductive material surrounding thedriveshaft to form a housing around the driveshaft.
 17. The medicalimaging system of claim 13, wherein the imaging transducer assemblyoperates electrically in parallel with the sensor.
 18. The medicalimaging system of claim 13, wherein the sensor includes an antennaportion having first and second terminals.
 19. The medical imagingsystem of claim 18, wherein the imaging transducer and the sensor sharethe first and second terminals.
 20. The medical imaging system of claim18, wherein the imaging transducer assembly has a first and secondtransducer terminal, the first transducer terminal being coupled to afirst wire and the second transducer terminal being coupled to a secondwire, the imaging transducer assembly and the sensor are coupled to thefirst and second terminals, the first wire is coupled with one of thefirst and second terminals and the second wire is coupled with the otherof the first and second terminals.
 21. The medical imaging system ofclaim 20, wherein the first wire is a center wire of a coaxial cable andthe second wire is an outer wire of the coaxial cable.
 22. The medicalimaging system of claim 21, wherein the first wire is one wire of acable with twisted pair wires and the second wire is the other wire ofthe cable with twisted pair wires.
 23. A catheter-delivered imaginginstrument system, comprising: a housing having a lumen; an imaginginstrument within the lumen of the housing; a means for automaticallytranslating the imaging instrument in a generally longitudinal directionbetween spaced apart positions relative to the housing within the lumen;a means for obtaining positional data of the imaging instrument duringthe translation of the imaging instrument; a means for obtainingcross-sectional images of the lumen during the translation of theimaging instrument; and a means for cross-correlating thecross-sectional images with the positional data.
 24. Thecatheter-delivered imaging instrument system of claim 23, wherein theimaging instrument is coupled with a radiopaque marker and thepositional data is obtained by monitoring the radiopaque monitor. 25.The catheter-delivered imaging instrument system of claim 23, whereinthe imaging instrument is coupled with a medical positioning sensor, andthe positional data is obtained by monitoring the medical positioningsensor.
 26. The catheter-delivered imaging instrument system of claim23, wherein the imaging instrument is an ultrasonic imaging transducer.27. The catheter-delivered imaging instrument system of claim 23,wherein the imaging instrument is coupled with a transmitter thattransmits positional data.